package LeetCode2018;

import java.util.HashMap;
import java.util.Map;

/**
 * Given nums = [2, 7, 11, 15], target = 9,
   Because nums[0] + nums[1] = 2 + 7 = 9,
   return [0, 1].
 * 数组中找出两个数之和等于target
 */
public class LeetCode001 {

    //方法一效率不高
    public int[] twoSum(int[] nums, int target) {
        int[] result = new int[2];

        for (int i = 0; i < nums.length; i++) {
            for (int j = i + 1; j < nums.length; j++) {
                if (nums[i] + nums[j] == target) {
                    result[0] = i;
                    result[1] = j;
                    return result;
                }
            }
        }
        result[0] = -1;
        result[1] = -1;
        return result;
    }

    //方法二，借助map
    public int[] twoSum2(int[] nums, int target) {
        int[] result = new int[2];
        Map<Integer, Integer> map = new HashMap<>();

        for (int i = 0; i < nums.length; i++) {
            if (map.containsKey(target - nums[i])) {
                return new int[]{map.get(target - nums[i]), i};
            }
            map.put(nums[i], i);
        }
        result[0] = -1;
        result[1] = -1;
        return result;
    }
}
